import java.util.Arrays;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 徐海涛
 * Date: 2022-02-13
 * Time: 11:27
 */
public class TestHeap {
    //堆 堆的底层是数组
    public int[] elem;
    public int usedSize;

    public TestHeap() {
        this.elem = new int[10];//new一个数组长度为 10；
    }
    /**
     * 向下调整函数的实现
     * @param parent 每棵树的根节点
     * @param len 每棵树的调整的结束位置 10
     */

    public void shiftDown(int parent,int len) {
        int child = 2 * parent + 1;
        //1.最起码 是有左孩子的，至少有1个孩子
        while (child < len) {
            if(child+1 < len && elem[child] < elem[child+1]) {
                child++;//保证当前左孩子最大值的下标
            }
            if(elem[child] > elem[parent]) {
                int tmp = elem[child];
                elem[child] = elem[parent];
                elem[parent] = tmp;
                parent = child;
                child = 2*parent+1;
            }else {
                break;
            }
        }
    }

        //创建一个大根堆
        public void createHeap ( int[] array){
            for (int i = 0; i < array.length; i++) {
                elem[i] = array[i];
                this.usedSize++;
            }
            //根据代码 显示的时间复杂度 看起来 应该是O(logn）但是实际上是O（n）
            for (int parent = (usedSize - 1 - 1) / 2; parent >= 0; parent--) {
                //调整
                shiftDown(parent, usedSize);
            }
        }


        private void shiftUp(int child) {
            int parent = (child - 1) / 2;
            while (child > 0) {
                if(elem[child] > elem[parent]) {
                    int tmp = elem[child];
                    elem[child] = elem[parent];
                    elem[parent] = tmp;
                    child = parent;
                    parent = (child-1)/2;
                }else {
                    break;
                }
            }
        }
        public  void offer(int val) {
           if(isFull()) {
               //扩容
               elem = Arrays.copyOf(elem,2*elem.length);
           }
           elem[usedSize++] = val;
           //注意这里传入的是usedSize -1;
            shiftUp(usedSize-1);
        }
        public boolean isFull() {
           return usedSize == elem.length;
        }

        //出队列
        public int poll() {
        if(isEmpty()) {
            throw new RuntimeException("优先级队列为空");
        }
        int tmp = elem[0];
        elem[0] = elem[usedSize-1];
        elem[usedSize-1] = tmp;
        usedSize--;
        shiftDown(0,usedSize);
        return tmp;
        }

        public boolean isEmpty() {
        return usedSize == 0;
        }


        public int peek() {
        if(isEmpty()) {
            throw new RuntimeException("优先级队列为空");
        }
        return elem[0];
        }

        //堆排序
    public void heapSort() {
        int end = usedSize-1;
        while (end > 0) {
            int tmp = elem[0];
            elem[0] = elem[end];
            elem[end] = tmp;
            shiftDown(0,end);//调整0小标这棵树结束位置是end
            end--;
        }
    }

    }






